The present invention concerns chlorinated polyethylene resins which are both semicrystalline and processible on conventional equipment without the need for plasticizers and other viscosity-reducing process aids. The present invention also concerns articles fabricated from compositions containing said resins, e.g., roofing membranes and wire and cable jackets.
Various processes for chlorinating olefin polymers in general and ethylene polymers in particular are known. The processes can generally be grouped into three types, namely solution chlorination, suspension chlorination and bulk chlorination. Chlorination of polyethylene in solution is known from U.S. Pat. No. 3,060,164. Chlorination in an aqueous suspension or an inert liquid is known from U.S. Pat. Nos. 2,592,763 and 3,454,544. Bulk chlorination, or chlorination in the absence of a liquid suspension agent or solvent, is described in U.S. Pat. Nos. 2,890,213 and 4,425,206 as well as in British Pat. No. 834,905.
Chlorinated polyethylene materials prepared by the three chlorination methods differ markedly in terms of physical properties, even if one starts with the same polyethylene resin and obtains the same overall chemically combined chlorine content. This appears to be due primarily to the more or less statistical distribution of chlorine in and along chlorinated polyethylene macromolecules. British Pat. Nos. 843,209 and 905,374 explain this phenomenon.
The term "lightly formulated", as used herein, refers to a compound containing 100 parts of chlorinated polyethylene resin, 3 parts of epoxidized soybean oil, 2 parts of calcium stearate and 0.5 parts of stearic acid.
The term "formulated low temperature brittleness value" refers to testing of ASTM D-746 type T-50 samples prepared from the physical blend detailed herein under the heading "Procedure for Preparing Roofing Membrane Test Samples".